The present invention relates to monitoring elevator doors and other portals of entry and egress. More particularly, the present invention relates to an apparatus and method for monitoring doors to ensure the safety of those entering and leaving through the doors.
The current method for monitoring elevator doors and the like is to use what is known as a two-dimensional (2D) array of light emitting diode (LED) devices that present a light curtain in the doorway. When a person or object crosses through the light curtain, photodetectors positioned to receive light from the LEDs sense a break in the light curtain, and the device triggers the doors to open. The problem with this method is that it does not give any information about what is about to happen, because it can only determine what is happening in the doorway at any time. U.S. Pat. No. 6,344,642 shows one form of 2D door control.
One solution that has been proposed is to use an additional group of LED devices that are angled outward from the elevator door into the lobby area. The LED devices are arranged so that light is bounced off something and received by a group of photodetectors. If the photodetectors detect a reflection, the system determines that something is on the way to the doorway and opens the doors.
The problem with this solution is that light will reflect off inanimate objects as well as people, generating a false positive or trigger. These false triggers can cause the system to open the doors fully, and then send a new signal when the doors start to close because no one entered through the door. The same inanimate object may cause the false trigger again multiple times. Elevators are programmed to shut down when the doors are reopened more than a predetermined number of times. This requires a service call by a mechanic, and, of course, not only takes the elevator temporarily out of service but increases maintenance costs.
In light of the foregoing, the present invention aims to resolve one or more of the aforementioned issues that can affect conventional elevator doors.